You can find your iPhone's IMEI number by going to Settings>General>About.

Have you tried logging into the browser version of the game through Facebook or the website?

This may sound silly and I apologise if I sound condescending here, but you may have simply deleted the Facebook account that you play Top Eleven on, from the Facebook section of your iPhone settings - I used to constantly switch accounts on there as I used to manage two teams from my iPhone.